1. Field of the Invention
The present invention relates to an apparatus for ejecting a cassette containing therein a recording/reproducing medium (to be referred to hereinafter for brevity as "a cassette" unless otherwise stated), and more particularly to a cassette ejection apparatus which ejects a loaded cassette by driving means such as a motor, a solenoid or the like.
2. Description of the Prior Art
A conventional magnetic disk unit which uses a 3.5-in. floppy disk incorporates a cassette ejection apparatus for ejecting a cassette out of the magnetic disk unit.
In such a cassette ejection apparatus, a loaded cassette can be ejected from the unit by actuating a switch with a light force because the apparatus is driven by a motor. Moreover, the cassette ejection apparatus can be controlled by software incorporated in a host apparatus which controls the magnetic disk unit.
The conventional cassette ejection apparatus ejects a loaded cassette under the condition that both an ejection switch (such as a push switch) and a cassette switch (such as a microswitch, a photodiode or the like) are turned on simultaneously. The ejection switch is turned on by an operator while the cassette switch is automatically turned on when a cassette is loaded into the magnetic disk unit or the like.
FIG. 1 is a time chart used to explain the mode of operation of a magnetic disk unit incorporating therein a cassette ejection apparatus substantially similar in construction to that disclosed in U.S. Pat. No. 4,628,376.
After a cassette is inserted in the cassette insertion slot of the magnetic disk unit at time T.sub.0 ', it is loaded in the magnetic disk unit at time T.sub.1 ' and the cassette switch is turned on.
When it is desired to eject the cassette out of the magnetic disk unit, the ejection switch is turned on manually at T.sub.2 '. Then under the condition that the cassette switch is kept turned on, a controller of the cassette ejection apparatus energizes an ejection motor. Then the ejection motor rotates a cam through one rotation so that the cassette ejection apparatus ejects the cassette out of the magnetic disk unit. One rotation of the cam is detected by a home-position switch, which is turned on when the cam is at home position.
The ejection of the cassette is accomplished before T.sub.3 ' at which time the cam has made one rotation and the home-position switch is turned on. When the home-position switch is turned on, the controller de-energizes the ejection motor.
As described above, by the operation carried out from time T.sub.0 ' to T.sub.3 ', the cassette is loaded in and ejected out of the magnetic disk unit.
In the case of a magnetic disk unit of the type described above, when foreign matter intrudes into the cassette loading mechanism or the cassette ejection mechanism, or when foreign matter, i.e., matter other than a cassette is inserted into the cassette insertion slot of the magnetic disk unit, such foreign matter must be removed. For this purpose, the magnetic disk unit must be provided with a mechanical emergency ejection mechanism in addition to the cassette ejection apparatus such as disclosed in U.S. Pat. No. 4,628,376. In order to obtain the force needed for discharging foreign matter, it is required to insert a pin or the like through a small hole of the magnetic disk unit to the emergency ejection mechanism or to push the bottom of the magnetic disc unit only to energize the emergency ejection mechanism. As described above, the emergency ejection mechanism operates independently of the cassette ejection apparatus.
The mode from T.sub.4 ' to T.sub.5 ' in FIG. 1 corresponds to a condition in which a cassette inserted into the cassette insertion slot of the magnetic disk unit cannot be correctly loaded therein because of the presence of foreign matter. It also corresponds to a condition in which foreign matter cannot be loaded into the magnetic disk unit because the inserted matter is foreign matter. Under these conditions, the emergency ejection mechanism of the type described above must be mechanically operated, but the cassette ejection apparatus is not activated at all. The reason is as follows. During the time period from T.sub.4 ' to T.sub.5 ' in FIG. 1, the cassette switch is not turned on for almost all conditions so that even when the controller detects that the ejection switch is kept turned on, the cassette ejection operation cannot be carried out because the cassette switch is not turned on.
As described above, in addition to the cassette ejection apparatus, the conventional magnetic disk unit must be provided with an independent mechanical emergency ejection mechanism. As a result, there arises the problems that the construction of the conventional magnetic disk unit becomes very complicated and the magnetic disk unit cannot be made compact in size and light in weight.